Tactical vehicles full of law enforcement officers drive through the search area for Dzhokar Tsarnaev, the one remaining suspect in the Boston Marathon bombing, in Watertown, Mass., on April 19, 2013.

Posted April 19, 2013, at 3:40 p.m.

From the relative safety of homes, workplaces and other places where people gather, the world came together to focus on Friday’s manhunt in Boston. The notion that a police search for one man could shut down a major city and many of its suburbs, affecting more than 1 million residents, adds to the shock waves that have reverberated from Boston since Monday’s bombings at the finish line of the marathon.

The shock strikes directly at the heart. Grief for lives lost and hope for an outcome with no more violence unite people from around the globe who seek to connect in person, via social media or any way possible. Those unable to believe what they were seeing in media coverage linked up to share empathy for Boston-area residents confined behind locked doors by the “shelter-in-place” order. Our hope is that the community created by that convergence can provide some comfort to those directly affected.

With shows of support from around the world, Boston residents seemed to be taking the first steps on a path to recovery. Then they awoke Friday in places they were ordered not to leave. Isolation and uncertainty magnified by the “shelter-in-place” order had to shake the sense of communal strength that grew with help from international signs of solidarity since Monday’s blasts. Now, those of us who tried to bolster Boston after Monday’s tragedy feel a new sense of helplessness. And images of tanks rolling along Massachusetts streets illuminate the severity of the threat.

Phalanxes of state troopers marching along familiar streets, SWAT teams deploying on college campuses and long lines of military-style vehicles with lights flashing create surreal images of an urban war zone, but they also remind us of the valor routinely displayed by police and first responders.

The heroism of people who head toward an emergency scene as others flee has been a recurrent theme since the marathon blasts. As former New England Patriot Joe Andruzzi, who carried an injured woman from the marathon bomb scene Monday and whose three brothers were members of New York City fire crews that responded to the 9/11 attacks, told the Boston Globe, “They are the people that don’t care about their safety and are worried for other people’s safety and survival.”

The selflessness and sacrifice that defines the work of first responders hits home as we mourn the death of Massachusetts Institute of Technology patrol officer Sean Collier, 26, who was shot in his cruiser, and hope that Massachusetts Bay Transportation Authority officer Richard Donahue Jr., who was wounded while attempting to apprehend two men suspected of placing the bombs, recovers quickly.

Seeing law enforcement officers — who started the night facing gunfire or had explosives thrown at them — continue to exude courage and control during hour after hour of nerve-snapping tension illuminates the human toll of the risk they encounter with every shift.

The events in Boston and the fire and explosion that claimed the lives of 11 first responders in West, Texas, have made it a profoundly tragic week.

Opportunities for proper tributes and reflection will come later. What we can offer is our heartfelt thanks and deep respect for the people who work to ensure public safety, continued encouragement to the people of Boston and this perspective from German folklorist Walter Anderson: “Bad things do happen; how I respond to them defines my character and the quality of my life. I can choose to sit in perpetual sadness, immobilized by the gravity of my loss, or I can choose to rise from the pain and treasure the most precious gift I have — life itself.”